1. Field of the Invention
The present invention relates to a solar cell and a method of manufacturing a solar cell.
2. Related Background Art
In place of bulk crystalline silicon solar cells which have been coming into wider use, thin-film solar cells using thin-film semiconductor layers as photo-absorber have been under development. Among them, thin-film solar cells employing p-type compound semiconductor layers containing Ib, IIIb, and VIb group elements as their photo-absorbing layers are expected to be next-generation solar cells, since they exhibit high energy conversion efficiencies and are less likely to be deteriorated by light (see Japanese Patent Publication Nos. 3249342, 3837114, and 3434259, Japanese Translated International Patent Application Laid-Open No. 2006-525671, Japanese Patent Publication Nos. 3468328 and 3337494, Japanese Patent Application Laid-Open No. 2004-047916, and Solar Energy Materials and Solar Cells 67 (2001 ):83 -88). Specifically, thin-film solar cells using CuInSe2 (hereinafter referred to as “CIS”) constituted by Cu, In, and Se or Cu(In1-a, Gaa)Se2 (hereinafter referred to as “CIGS”) partly replacing In, which is a IIIb group element in CIS, with Ga as their photo-absorbing layers have yielded high conversion efficiencies (see Prog. Photovolt: Res. Appl. (2008), 16:235-239).